Democratic and Republican senators joined a former deputy chairman of the Joint Chiefs of Staff on Tuesday in urging the Obama administration to make public more information about its top-secret targeted killing program amid questions about the legality and effectiveness of hundreds of CIA drone strikes in Pakistan and elsewhere.

Democratic and Republican senators joined a former deputy chairman of the Joint Chiefs of Staff on Tuesday in urging the Obama administration to make public more information about its top-secret targeted killing program amid questions about the legality and effectiveness of hundreds of CIA drone strikes in Pakistan and elsewhere.

“More transparency is needed to maintain the support of the American people and the international community” for drone strikes, said Sen. Dick Durbin, D-Ill., a key Obama ally and the chairman of the Constitution subcommittee of the Senate Judiciary Committee.

The White House refused to send a witness to the Senate’s first open hearing on the issue despite President Barack Obama’s vow to be more forthcoming about a counterterrorism weapon that has become a despised symbol of U.S. foreign policy in many parts of the world.

“I am disappointed that the administration declined to provide witnesses to testify at today’s hearing,” Durbin said. His frustration was echoed by several other Democrats and Republicans.

The hearing came nearly 12 years after the United States launched its first drone strike, underscoring what some legal scholars and civil and human rights experts have criticized as insufficient oversight by Congress.

But the killings of four U.S. citizens – three of them accidentally – in Yemen and Obama’s appointment of John Brennan, his former counterterrorism chief and overseer of the targeted killing program, to head the CIA have increased pressure on lawmakers to examine the use of drones in Pakistan, Somalia, Yemen and Libya.

The program remains shrouded in secrecy. The administration insists that civilian casualties have been “exceedingly rare” despite a huge expansion in strikes under Obama. Independent studies put the number of strikes since 2001 at more than 360 and estimate that as many as 3,533 people, including up to 884 civilians, have died, the vast majority in CIA operations in Pakistan’s tribal area.

Earlier this month, McClatchy published a review of top-secret U.S. intelligence reports showing that at their height in 2010-2011, scores of CIA drone strikes killed hundreds of unidentified lower-level Afghan, Pakistani and “other” militants in Pakistan. The finding contrasts with the administration’s assertion that it targets only known “senior operational leaders” of al Qaida and associated groups involved in the Sept. 11, 2001, terrorist attacks who are plotting “imminent” violent attacks on the United States.

In his opening statement, Durbin noted that the Constitution gives Obama the “unique responsibility to protect and defend our country.” His authority to do so, however, is based on the rule of law, “which has been abused during times of war,” Durbin said, an apparent reference to Bush administration detainee interrogation methods that many experts consider torture.

Moreover, while the CIA’s use of drones against al Qaida and other terrorist targets in remote locations has made targeted killing “less costly” because U.S. troops don’t have to be employed, “there are long-term consequences, especially when these airstrikes kill innocent civilians.”

“That’s why many in the national security community are concerned that we may undermine our counterterrorism efforts if we do not carefully measure the benefits and costs of targeted killing,” Durbin said – a reference to concerns that civilian casualties have helped militant groups recruit new members.

Farea al Muslimi, a U.S.-educated activist from Yemen, testified that drone strikes have killed many civilians in his country, aiding al Qaida’s regional affiliate, al Qaida in the Arabian Peninsula, by appearing to affirm its propaganda that the United States is waging war against ordinary Yemenis.

“The drones have simply made more mistakes than AQAP has ever done,” he said.

Durbin called on the administration to make public more details about “its legal authority to engage in targeted killing and the internal checks and balances involved in U.S. drone strikes.”

The administration also should work with Congress to address “serious and challenging questions,” he said. Those should include how it determines when an American citizen can be targeted, the basis for drone strikes in areas that aren’t active battlefields, and the “moral and legal responsibilities” that the United States might have for confirming civilian casualties and compensating their families.

Sen. Ted Cruz, R-Texas, a tea party-backed freshman, said he worried that drone attacks had eliminated terrorists who, had then been captured and interrogated, could have provided “actionable intelligence” on plots to attack the United States. He said that “the real scope of this hearing and of the concern is on the scope of federal power.”

Sen. Lindsey Graham, R-S.C., an Air Force Reserve officer, said he supported bringing more transparency to the targeted killing program, but he opposed a proposal by some legal scholars and lawmakers for the creation of a special court to approve targeting decisions before they could be implemented.

“If you want to talk about transparency, count me in,” said Graham, who added that when it comes to allowing “a bunch of unelected judges” to make such “wartime” decisions, “count me out.”

In limited public statements and a leaked Justice Department white paper, the administration insists that drone strikes comply with U.S. and international laws, including the laws of war. Moreover, the administration contends that the strikes are justified by an “inherent right of self-defense” and a congressional resolution passed after the 9/11 attacks that authorized the president to use lethal force to fight al Qaida and associated groups that aided in the attacks.

Retired Marine Gen. James Cartwright, the vice chairman of the Joint Chiefs of Staff from August 2007 to August 2011, said that drones are an effective and accurate method for eliminating dangerous terrorists. But he said that he’s worried that the administration’s refusal to disclose the legal basis and detailed procedures for how targets are identified away from active battlefields have cost the United States “the moral high ground.”

In his prepared remarks, Cartwright said that “legitimate questions remain about the use, authorities and oversight of armed drone activities” away from active battlefields.

“We should now ask: Are the use, authority and oversight protocols actually providing us with the safeguards we want?” asked Cartwright, the vice chairman of the Joint Chiefs of Staff from August 2007 to August 2011.

Cartwright called on Obama to establish a government task force to evaluate secret drone strikes, including the extent of civilian casualties and their impacts on communities; the effectiveness of precautions used to avert such casualties; and the means by which the results of strikes are assessed. An unclassified version of the task force’s final report should be made public, he said.

Cartwright said the CIA also should publicly acknowledge its role in drone operations outside Afghanistan, establish procedures for declassifying information on those operations after they’re over, and provide information to Congress on the impact of drone strikes on civilians.

Rosa Brooks, a Georgetown University Law Center professor who served as a Pentagon adviser during the height of the drone strikes, questioned the legality of drone strikes away from active battlefields, saying that the targeted killing policy “is on the verge of doing significant damage to the rule of law.”

One reason, she said in her prepared statement, is that the administration has refused to detail publicly the still top-secret legal underpinnings of targeted killings and the internal procedures used to determine who can be targeted.

She pointed to the administration’s contention that the United States is in a global war with al Qaida and its terrorist allies.

“On that basis, they (the administration) assert that the law of war is applicable – in any place and at any time – with regard to any person the administration deems a combatant,” Brooks said. “The trouble is no one outside a very small group within the U.S. executive branch has any ability to evaluate who is and who isn’t a combatant.

“What’s more, targeting decisions in this nebulous ‘war’ are based largely on classified intelligence reporting,” she continued. “As a result, administration assertions about who is a combatant and what constitutes a threat are entirely non-falsifiable, because they’re based wholly on undisclosed evidence.”